One-channel time-reversal in chaotic cavities: Experimental results

Experiments are presented that show the feasibility of reconstructing a poi nt source using acoustic time-reversal with a single transmitter/receiver. The propagation medium is a closed 2-D silicon cavity with chaotic ray dyna mics and negligible absorption. Injection of a short pulse at one point yie lds a long signal at a second one; by reversing a part of this signal, we o btain a focus at the initial injection point. The characterization of the f ocus was observed by scanning with an optical interferometer and by measuri ng the signal at the focal spot. With circular converging wavefronts, the r econstructed focus was excellent (corresponding to an aperture of 360 degre es), but not perfect, The increase in quality of the focus with growing len gth of the reversed signal is described by a statistical ray model. Despite the irreversibility in classical chaos (due to strong sensitivity to initi al conditions), the underlying chaotic ray dynamics is useful in this case. (C) 1999 Acoustical Society of`America. [S0001-4966(99)04301-5].